Over-concentrated fixer

Hi all,

I have made a mistake in mixing up Ilford Rapid fixer - I added the concentrate to a graduate that already had some water
in it (and I didn't make a note of how much water, or how much concentrate I had to begin with - bad record keeping all through). It's between 1+1 and 1+3 concentration.

Clearing time is about 30 seconds. I read somewhere that clearing time less than a minute indicates that the solution
is too concentrated. I am using a 2 bath fixing procedure (both clear in 30 seconds - this was a fresh batch of chemicals), and
am doing 90 seconds in each. Is that too much/too little?

The first set of negatives using this fixer seemed to be thinner (To my eyes - not a proper measurement in any sense. It
might all be in my head, given that I know I messed up the fixer) than what I considered normal from earlier experience with
the same film/dev/fixer combination (Arista Premium 100/D-76/Ilford Rapid fixer).

Should I try to rectify the over-concentration issue by diluting the solutions further?

Also perhaps related to the concentration in some way are the following:

(a) The fixer turned light purple. I have never seen that happen with this film before. I though that this is usually the antihalation layer/dye, and would have gone away with the developer.
(b) There is a white sediment/coating at the bottom of the fixer bottles. No floating particles in the solution, and the sediment
seems stuck to the bottom. The fixer bottles (full) have been stored at around 15 degrees C, for about 6 months since the faulty mixing. The fixer isn't dead yet, as the clearing test shows, but perhaps some chemical change has happened?

I get a film (Delta 100) clearing time of around 40 seconds in fresh Ilford Rapid Fixer 1+4.

The Ilford data sheets says it can be used either 1+4 or 1+9 for manual application - which of course means it can be used at in-between dilutions, too. So if I were you, I would dilute your unknown concentration 1+1.5 with water (in other words, if you have 1 litre of mixed fixer then add another 1.5 litres of water). This means the actual concentration will be between 1+4 (if it was originally 1+1) and 1+9 (if it was originally 1+3). Then I would do a clip test, and use it with a fixing time of at least twice the clearing time found in the clip test (you can split this total time equally between the two baths).

Your fixer is more dilute rather than over-concentrated. For example, if you put concentrate up to the 500 ml mark and there was already 50 ml of water there then you used 450 ml of concentrate rather than the 500 ml you wanted. The solution is more dilute not stronger.

A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

Andrew: Thanks for the suggestion - I can get to _some_ concentration between 1+4 and 1+9, and then go with the clearing time test again.

Gerald: I didn't follow the mixing recommendations on the concentrate bottle after I messed it up - so what I have right now isn't a "more dilute" version of what I ought to have had.

I compared the negatives with my earlier samples, and the latest ones definitely have a purple cast to them.

Just eyeballing the latest negatives with earlier "known good" versions, it looks like the overall density is pretty close, but the negatives are less contrasty than what I was used to. Reviewing my notes, it looks like I made one further mistake. Normally I would start my solutions at 70 degrees F, while using the dev times for 68 degrees (the Ilford doc on processing suggests this since the temperature would fall slightly during development - I am using plastic tanks, so I can't control the temp. once the solutions are poured in). But the latest set of negatives was done starting at 68 degrees. Maybe that is leading to slight underdevelopment, and hence the loss in contrast?

Sorry but your description wasn't clear. You could use a hydrometer to determine how much more water to add. Another possibility is to mix up a 100 ml of fixer and weigh it. This will give you the specific gravity. You can use this technigue to determine how much more water to need to add. But offhand I wouldn't worry about the fixer being a bit too strong. It's not going to hurt anything.

Last edited by Gerald C Koch; 07-23-2012 at 04:57 PM. Click to view previous post history.

A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

I would discard the unknown concentrated fixer, and make a new batch more carefully. Who said that gaining experience is free ? Besides, putting at risk film, which come from a very labor intensive, time consuming activity, is self defeating.

The suggestion above to weigh it is what I have done when making a similar mistake. 100mL of water weighs 100g. 100mL of fixer concentrate weighs 134g. For 1+4 you're looking for 100mL weighing about 106.8g. If it's not the right concentration it's unlikely to make much difference anyway.

Edit: I've just read the posts properly and if there's sediment it means that the fixer is partially decomposed. Maybe it's ok for film (you can tell by looking at the results) but I'd not use it for paper.